And if you really wanted to have something that was Cubase or Nuendo, why not just buy that? It is out there and it will most likely have a lot less bugs than anything I would write in PD that tried to emulate it.
check out ardour, its an amazing free application, its getting to the point where its competitive with the big guys:
trying to turn pd into cubase is kind of a dead end and misses the point of pd really. i mean, you should be able to do anything you'd want to within pd, but it will always be utterly different in work flow and general character than dedicated sequencers.